Various underwater mining devices, dragheads or earth moving suction nozzles have been provided for the purpose of excavating underwater by means of suction, with or without jet diggers, or for mining or in situ disintegration of material below the surface of the water. These devices usually form part of the large apparatus which is moved about as part of large excavating equipment. One example of that type of hydraulic suction nozzle is shown in the U.S. Pat. No. 2,774,569 issued Dec. 18, 1956 and entitled "Earth Moving Hydraulic Suction Nozzles" and wherein the clogging of these nozzles by rocks or other objects is acknowledged as a chief cause of difficulty. In that particular patent, the tubular nozzle has strainer bars and a helical spring at its inlet end in an attempt to remedy that difficulty, however, such an arrangement tends in itself to restrict the in-flow of the material to be removed and becomes clogged itself. Another example of an "Underwater Mining Device" is shown in the U.S. Pat. No. 2,605,090 issued July 29, 1952. That device can be used only for picking up small objects, such as particles of gold or other precious metals underwater and has a very small nozzle area to suction pipe area for that purpose.
A third type of prior art device is shown in U.S. Pat. No. 2,280,066 which issued Apr. 21, 1942 entitled "Draghead For Dredging Apparatus" in which the draghead is used and a central water supply is used to relieve the pressure of the draghead on the surface of the river channel to effect a scouring action.
The above and other prior art devices have had certain shortcomings, among which is the fact that they are incapable of being firmly and positively controlled by the operator who must hold the dredge head in his hands and work for considerable periods of time in a sometimes dark location and under difficult circumstances.
Other type prior art dredging apparatus such as air lifts or hydraulic lifts have not been satisfactory because, among other things, of their lower head capabilities, poor capacity and inability to use them in any position.